JPH03231845A - Laminated polyester film - Google Patents

Abstract

PURPOSE:To improve the adherence and solvent resistance of hardened film by a method wherein the silicone resin hardened case is produced by irradiating ultraviolet rays under specified conditions over ultraviolet-curing silicone resin, which is applied on at least one side of polyester film. CONSTITUTION:Coating liquid, the main component of which is ultraviolet-curing silicone resin, is applied onto at least one side of polyester film. Next, while the film is cooled below the temperature higher than the glass transition tempera ture (Tg) of polyester by 20 deg.C, ultraviolet rays are irradiated over said coated surface under the condition that the integral amount E(mJ/cm<2>) of ultraviolet rays having the wavelength of 330 - 390 nm satisfies the formula I, in which T is the thickness of the polyester film in mum, so as to produce silicone resin hardened case in order to obtain laminated polyester film. As the ultraviolet- curing silicone resin, oligomer or polymer having the siloxane structure with light-reactive group at the terminal is used.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a laminated polyester film, and more specifically, a polyester film laminated with an ultraviolet curable silicone resin cured film, in which the curing of the silicone resin is specified. This invention relates to a laminated polyester film in which thermal distortion of the polyester film is suppressed and the adhesiveness and solvent resistance of the cured silicone resin film are improved by carrying out the process under the following conditions.

In particular, the laminated polyester film of the present invention can be used as a release film or a cassette sheet (sliding sheet) for magnetic tape.
It is suitable as a film for use.

[Prior art and problems]

Films for mold release and magnetic tape cassette sheets (sliding sheets) generally use a polyester film as a base film, and a cured silicone resin film is formed on the surface of the base film.

As the silicone resin, a heat-curable type in which a silicone resin raw material is subjected to addition polymerization in the presence of a platinum-based catalyst is widely used.

However, the above-mentioned type of silicone resin has the problem that it is not sufficiently cured by short-time heat treatment, and that thermal distortion occurs in the base film if long-time heat treatment is performed.

In addition, when exposed to air for a long time, there is a problem that the adhesion of the cured film to the base film and the solvent resistance of the cured film itself deteriorate.

On the other hand, in addition to the above-mentioned type, there is also a heat-curing type in which silicone resin raw materials are condensed and polymerized in the presence of an organotin-based catalyst, but this heat-curing process is even slower and tends to cause problems in processing.

In recent years, ultraviolet curable silicone resins have been developed and are being used for release paper applications, but sufficient results have not been obtained regarding their application to polyester films. this is,
This is because the curing conditions for the ultraviolet curable silicone resin coating liquid applied to the surface of the polyester film have not been established.

In other words, in general, UV-curable silicone resins can be cured in a shorter time than heat-curable versions of the same resin, but they generate a large amount of heat when exposed to strong UV rays. However, there is a problem in that the base film becomes highly thermally distorted. On the other hand, in order to avoid this problem, ultraviolet curing treatment under mild conditions can be considered, but it is regrettable that excellent film properties cannot be obtained by such treatment.

[Structure of the invention]

In view of the above circumstances, the present invention was completed as a result of repeated studies on the curing conditions of an ultraviolet curable silicone resin coating liquid applied to the surface of a polyester film. Both are laminated polyester films formed by coating one side with a coating liquid containing an ultraviolet curable silicone resin as a main component and irradiating the coated surface with ultraviolet rays to form a silicone resin cured film, wherein the silicone resin cured film is , the polyester film in the ultraviolet irradiation part is heated to its glass transition point temperature (Tg) +20
UV rays on the coated surface while cooling to a temperature below 3°C.
Cumulative light amount E (mJ/cnf) for wavelengths of 30 to 390 nm
This can be easily achieved by using a laminated polyester film characterized in that it is formed by irradiating ultraviolet rays under conditions that satisfy the following formula.

(In the above formula, T is the thickness of the polyester film (μm)
The present invention will be described in detail below.

The polyester of the polyester film in the present invention is polyethylene terephthalate in which 80 mol % or more of its constituent units are ethylene terephthalate or polyethylene naphthalate in which ethylene naphthalate is present.

The polyester film of the present invention may contain inorganic particles, organic particles, organic lubricants, antistatic agents, stabilizers, dyes, pigments, and organic polymers as a composition, if necessary. In order to impart slipperiness to a polyester film, fine particles are included in the film composition, but the type, size, and composition of the protrusion-forming agent may be adjusted depending on the required properties such as slipperiness and transparency of the product to be used. The amount is selected accordingly.

In addition, the properties of the polyester film constituting the substrate, such as orientation, crystallinity, mechanical properties, and dimensional stability, may be determined by those skilled in the art according to the required properties of the product in which the laminated polyester film of the present invention is used. This can be achieved by selecting manufacturing conditions.

The coating liquid in the present invention has an ultraviolet curable silicone resin as a main component.

The above-mentioned silicone resin generally consists of an oligomer or polymer having a siloxane structure having a photoreactive group at the end. The coating liquid contains a photopolymerization initiator and, if necessary, a sensitizer, thereby imparting radical reactivity.

In addition, the coating solution in the present invention contains a photoreactive vinyl compound to improve the properties of the cured film, and inorganic fine particles such as silica, silica sol, alumina, and alumina sol to improve the adhesion and slipperiness. , zirconium sol, kaolin, talc, calcium carbonate, titanium oxide, barium salt, carbon black, molybdenum sulfide, antimony oxide sol, etc., and if necessary, a foaming agent, a coating property improver, It may contain a thickener, an antistatic agent, an organic lubricant, an organic polymer particle, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, a pigment, and the like.

Coating liquids containing the above-mentioned ultraviolet curable silicone resin as a main component are commercially available in various brands from various companies.
B, KS-5503A/B.

KS-5514A/B, KNS-5003A/B.

X-62-5039A/B, X-62-5040A/
B, X-62-5051A/B.

X-62-7296A/B, DKX2-222/223 manufactured by Dow Corning ■, U manufactured by Toshiba Silicon ■
V-9300/9310C etc. can be suitably used.

The above-mentioned coating liquid is diluted with an organic solvent as necessary and applied to the surface of the polyester film.The coating method is shown in "Coating Method" written by Yuji Harasaki, published by Maki Shoten, 1979. , a reverse roll coater, a gravure coater, a rod coater, an air doctor coater, or a coating device other than these.

Generally, a biaxially stretched polyester film is used, and a coating liquid is applied to this.
In cases where dilution of the coating liquid with an organic solvent is not required, a so-called coating and stretching method may also be employed. In this case, a method in which a coating solution is applied to an unstretched polyester film and biaxially stretched sequentially or simultaneously; a method in which it is applied to a -axially stretched polyester film and further stretched in a direction perpendicular to the previous uniaxial stretching direction. Alternatively, there is a method of re-stretching a biaxially stretched film having these coated layers, or a method of coating a biaxially stretched polyester film and further stretching in the transverse and/or longitudinal direction.

The above-mentioned stretching process is preferably carried out at 60 to 130°C, and the stretching ratio is at least 4 times or more in terms of area ratio, preferably 6 to 20 times. The stretched film is 15
Heat treated at 0-250°C.

Furthermore, in the maximum temperature zone of the heat treatment and/or the cooling zone of the heat treatment outlet, the temperature is 0.2 to 20 in the longitudinal and transverse directions.
% relaxation is preferred.

In the present invention, the coating liquid may be applied to only one side of the polyester film, or may be applied to both sides.

When it is coated only on one side, a cured film other than the silicone resin cured film may be formed on the opposite side, if necessary, to impart other properties to the laminated polyester film of the present invention.

In addition, in order to improve the applicability and adhesion of the coating liquid to the film, the film may be subjected to chemical treatment or electric discharge treatment before application.

The thickness of the polyester film coated with the coating liquid obtained as described above is preferably in the range of 3 to 500 μm. On the other hand, the thickness of the cured film is appropriately selected depending on the intended use, and is generally selected from a wide range of 0.01 to 6 g/m as the amount of coating after curing. In particular, in the case of release films or films for magnetic tape cassette sheets (sliding sheets), which are preferred applications of the polyester film according to the present invention, 0.05 to 0.6 g
It is preferable to set it in the range of /rrr. Coating amount is 0.05g/
When it is less than rrr, the solvent resistance of the coating film is low and it is 0.6
If it exceeds g/rrr, the film has low slipperiness, and in either case, it is difficult to adapt to the above-mentioned uses. The preferred coating weight for this application is in the range of 0.1 to 0.3 g/rd.

The most important feature of the present invention is that the coating liquid applied to the surface of the polyester film as described above is cured under specific conditions.

Curing of the coating liquid by ultraviolet irradiation is carried out after the coating liquid has dried, but if the coating stretching method is adopted, it is possible to dry the coating liquid at the same time as stretching, so drying the coating liquid may be omitted. .

In the present invention, the ultraviolet irradiation is carried out at the glass transition point (Tg) of the polyester film in the ultraviolet irradiation area.
) While cooling to a temperature of +20°C or less, the cumulative amount of ultraviolet light E (mJ/c
It is important to perform ultraviolet irradiation under conditions where rl) satisfies the following formula.

(In the above formula, T is the thickness of the polyester film (μm)
In other words, the ultraviolet irradiation device is equipped with a selective light reflector called a cold mirror and a selective light transmitter called a cold filter in order to effectively utilize only the ultraviolet light and remove the heat rays that are generated at the same time. Furthermore, depending on the equipment, the distance between the ultraviolet irradiation lamp and the object to be irradiated can be changed as appropriate. Therefore, when curing the coating liquid by irradiating ultraviolet rays, it is possible to reduce the degree of irradiation depending on the degree of thermal distortion that the polyester film receives. However, in this case, the coating liquid on the surface of the polyester is not sufficiently cured, and as a result, the superiority of the ultraviolet-curable silicone resin coating film is not fully expressed. In contrast, in the present invention, the cumulative amount of ultraviolet rays necessary to form an excellent silicone coating film is confirmed, and irradiation is carried out while maintaining this amount of light.On the other hand, a cooling means is provided to prevent thermal distortion of the polyester film. The aim is to prevent this.

The above-mentioned equation regarding the cumulative light amount was confirmed by the inventor as the necessary irradiation amount to fully express the superiority of the silicone resin coating in the wavelength range effective for curing the ultraviolet curable silicone resin. It is.

For ultraviolet irradiation in the present invention, basically, conventional ultraviolet irradiation equipment can be used, which is equipped with reflective mirrors of various shapes, the aforementioned cold mirror, etc. to effectively reflect and condense ultraviolet rays. . As the ultraviolet lamp, a rod-shaped high-pressure mercury lamp or metal halide lamp whose effective emission length is wider than the width of the coating liquid on the polyester film is used, but a high-pressure mercury lamp is preferred.

The cooling means of the ultraviolet irradiation device cools the polyester film in the irradiation part to its glass transition point temperature (Tg) +208
There are no particular restrictions as long as the means can cool to a temperature of C or below, but a cooling means with less loss of ultraviolet rays and high cooling efficiency is a water-cooled plate or water-cooled roll provided on the back side of the polyester film. Cooling measures are recommended.

In order to perform cooling more efficiently, it is preferable to apply cooling air to the polyester film in the ultraviolet irradiation section.

Also, the cumulative amount of ultraviolet light E (mJ/crl)
If this is less than the value of 20 (ffog T)2, the silicone resin is insufficiently cured;
00(j7ogT)'', thermal distortion of the polyester film cannot be effectively prevented even by applying a cooling means, and no further improvement is observed in the properties of the resulting cured film, resulting in lower energy costs. becomes large.

Therefore, the preferable integrated light amount is within a range that satisfies the following formula.

〔Example〕

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

In addition, in the following examples, the calculation of the integrated light amount and the evaluation of the physical properties of the obtained film were performed by the following method.

■ Calculating the cumulative light amount Ushio Inc.'s cumulative light meter (Unimeter UIT-10)
2) and a light receiver (UVD-365PD), calculations were performed in mJ/cf units according to the following procedure.

A light receiver is set on the low-speed running film, and a UV irradiation energy measurement label (@Tomoe Paper Mills UV Checker) is attached to perform measurement, and the constant values on both sides are compared and verified.

The cumulative amount of light for a high-speed running film was calculated by attaching a UV checker to the film and comparing the measured value with the above direct measured value.

Incidentally, it was found that the cumulative amount of light received by the film was inversely proportional to the film running speed under constant irradiation conditions.

(2) Coating film amount Based on the solid content concentration of the silicone resin coating solution and the solution consumption I, the average coating amount was determined based on the formula below and was used as the coating film amount.

■ Film thermal distortion Judgment was made visually according to the following criteria.

○: Good condition with small distortions such as heat wrinkles △: Slightly noticeable distortions such as heat wrinkles ×: Significant heat wrinkles, heat walnuts, etc. ■ Paint film adhesion Rub the silicone paint film with your finger, and the paint film turns white and falls off. I looked into it. In addition, cellophane adhesive tape was applied to the rubbed surface, and the release properties of the adhesive surface when the tape was peeled off were examined. The judgment criteria are as follows.

○: Good with almost no falling off of the coating film or deterioration of the mold release properties △: Partial falling off of the coating film was observed, and areas with poor mold release properties were observed when the adhesive tape was removed ×: The coating film did not fall off. In Table 1, the "initial" evaluation period indicates the characteristics immediately after the silicone coating and hardening treatment, and the "after air exposure" indicates the characteristics after the silicone coating and hardening treatment. The surface was left in the air and the properties investigated after one week are shown.

■ Solvent Resistance of Paint Film Using gauze impregnated with toluene, rub the silicone paint film repeatedly 10 times while pressing down with a pressure of about 100 g, and then air dry. Attach cellophane adhesive tape to the rubbed surface and perform an evaluation similar to the evaluation of paint film adhesion.

■ Smoothness Hand-wrap a silicone-coated film approximately 1 m long into a cylindrical shape with a diameter of 5 cm. Check whether the rolled film can easily slip between the films. The judgment criteria are as follows.

○: Sliding occurs with almost no resistance between the films, and has very good slipping properties. △: Sliding properties are comparable to that of an uncoated film, but the silicone coating surface is slightly sticky. ×: Silicone coating surface Example 1 UV-curable silicone resin paint X- manufactured by Shin-Etsu Chemical Co., Ltd.
12-5040A and curing agent component X-12-5040
B was prepared at a weight ratio of 20/1, and dissolved in a diluting solvent having a weight ratio of toluene/methyl ethyl ketone = 1/1. Next, using a film coater, a 25 μm thick biaxially stretched polyester film (T'25.Tg manufactured by Diafoil ■) was coated.
After drying the solvent in a drying oven with a 120°C atmosphere, the irradiated film is exposed to cooling air, and is equipped with a cold mirror and a cold filter, as well as a water cooling plate on the back side. The sample was passed through an ultraviolet irradiation facility with a

The film running speed is 40 m/min, input 1
The mixture was cured by irradiation with ultraviolet rays using two 20 W/cm high-pressure mercury lamps to obtain a polyester film laminated with a cured silicone resin film having a coating weight of 0.2 g/m'. The film temperature at the exit of the ultraviolet irradiation equipment was 70°C.

In addition, separately confirmed by running an uncoated film, 33
The cumulative light amount in the 0-390nm sensitivity range is approximately 130 mJ
/+ffl.

The obtained laminated polyester film was evaluated for physical properties, and the results are shown in Table 1 along with the curing conditions.

Examples 2 to 7 and Comparative Examples 1 to 6 As shown in Table 1, a cured silicone resin film was laminated in the same manner as in Example 1, except that the type of silicone resin, the thickness of the polyester film, and the curing conditions were changed. A polyester film was obtained.

Physical properties of the obtained laminated polyester film were evaluated, and the results are shown in Table-1.

Comparative Example 7 Addition polymerization type thermosetting silicone resin paint KS 772 manufactured by Shin-Etsu Chemical Co., Ltd. and platinum catalyst PL-3 at a weight ratio of 20
10.2 and toluene/methyl ethyl ketone-1
/I weight ratio of diluting solvent. Next, using a film coater, it was coated on one side of a 25 μm thick biaxially stretched polyester film (Diafoil (T'25 manufactured by Kiki).
Solvent drying and curing for 9 seconds were carried out in a drying oven at 50° C. to obtain a polyester film laminated with a cured silicone resin film having a coating weight of 0.2 g/rrr.

We evaluated the physical properties of the obtained laminated polyester film,
The results are shown in Table-1.

(Hereinafter, blank space) [Effects of the Invention] According to the present invention described above, by establishing the curing conditions for the ultraviolet curable silicone resin, an excellent cured film that fully expresses the characteristics of the silicone resin can be formed on its surface. The present invention has great industrial value.

Claims (1)

[Claims] (1) A laminated polyester film formed by coating at least one side of a polyester film with a coating liquid containing an ultraviolet curable silicone resin as a main component, and irradiating the coated surface with ultraviolet rays to form a cured silicone resin film, The silicone resin cured film cools the polyester film in the ultraviolet irradiation area to a temperature below its glass transition temperature (Tg) + 20°C, while suppressing ultraviolet rays of 330 to 30°C on the coated surface.
A laminated polyester film, characterized in that it is formed by irradiating ultraviolet rays under conditions where the cumulative amount of light E (mJ/cm^2) at a wavelength of 90 nm satisfies the following formula. 20<E/(logT)^2<300 (In the above formula, T is the thickness of the polyester film (μm)
)